I connected my intrface board as per the diagram but I don't get a blinking light. I get a solid red light. What could cause this?

The Mach3 USB controller will light a solid red light when the controller is properly connected to the computer, and mach3 is in the ready mode (reset pressed to engage the machine). When an arrow key is pressed to move an axis, the red LED will blink rapidly showing there is communication to the controller. If it does not blink rapidly, then check the motor output and confirm that the axes are enabled. Also, confirm you are in jog mode (located in the program run tab). You can also try using the built-in MPG by pressing the TAB key and clicking on the axis letters to move the axes.